1. Field of the Invention
This invention relates to operating devices such as vehicle operating pedal devices or the like, and more particularly, to improvement of a load-sensor-equipped operating device having a load sensor for electrically detecting an operating force.
2. Description of the Related Art
Load-sensor-equipped operating devices have heretofore been known with one type including (a) an operating member displaceably operate; (b) a reactive member; (c) at least one pivotably connecting section; and (d) a load sensor. An operating force of the operating member is transmitted to the reactive member, on which a reactive force acts according to operating force. At least one pivotably connecting section is interposed between the operating member and the reactive member to interconnect a pair of members to be pivotable, relative to each other about a connecting pin, through which the operating force is transmitted. The load sensor electrically detects such an operating force.
Patent Publication 1 (U.S. Pat. No. 5,563,355) discloses a vehicle brake pedal device, which represents one example of the load-sensor-equipped operating device. This load-sensor-equipped operating device is structured such that a pushrod (reactive member) protruding from a master cylinder, is connected to the connecting pin extending from an operating pedal at side portions thereof, to be relatively movable in an axial direction. Thus, a displacing amount of the pushrod relative to the connecting pin against an urging force of a spring is detected by a sensor.
With such a device disclosed in Patent Publication 1, however, since the pushrod needs to be formed with an elongate hole for connection to the connecting pin to allow the pushrod to move relative to the connecting pin axially, no usual pushrod can be used intact. Further, since the pushrod is pivoted i.e. pivotable relative to the connecting pin with a depressing displacement of the operating pedal, the spring urging the pushrod and the sensor detecting the displacement amount are required, to be mounted pivotably with respect to the connecting pin. As a result, the device becomes complicated in structure.
In addition, the pushrod, the spring and the sensor are placed on the operating pedal at the side areas thereof, so that the brake pedal particularly needs to take a robust i.e. rigid structure for ensuring a stable operating condition. This results in an increase in size of the device as a whole, causing an increase in production cost.
As shown in FIGS. 21A and the 21B, on the contrary, a technology has been taken into consideration to provide a structure, not known, for mounting a load sensor on a connecting position of a clevis pin in a compact layout. FIGS. 21A and the 21B are views showing an operating pedal device 200 for a vehicle service brake. FIG. 21A is a front view and FIG. 21B is an enlarged view showing a cross sectional view taken on line XXIA-XXIA of FIG. 21A.
A plate-like operating pedal 16 is mounted on a pedal support 12, integrally fixed to a vehicle, to be pivotable about an axis of a support shaft 14 that extends in an approximately horizontal direction. The operating pedal 16 depressable in operation by a driver in response to a braking requirement, has a lower distal end including a depressable portion (pad) 18, and an intermediate portion to which an operating rod 22 of a brake booster is connected via a pivotably connecting section 20. The pivotably connecting section 20 includes a U-shaped clevis 24, integrally connected to the operating rod 22 at one end thereof by means of a screw coupling or the like, and a clevis pin 26 mounted on the operating pedal 16 in parallel to the support shaft 14. The pivotably connecting section 20 is configured to connect the operating rod 22 and the operating pedal 16 to each other pivotably about an axis of the clevis pin 26.
The clevis pin 26 corresponding to the connecting pin, has both axial end portions, protruding from the operating pedal 16 on both sides thereof, which are retained with the U-shaped clevis 24 via a snap ring or a retaining pin or the like in non-escaping fashion. An output corresponding to the operating force acting on the operating pedal 16 is transmitted to the operating rod 22 via the pivotably connecting section 20, and the resulting reactive force equivalent to the output acts on the operating rod 22 by means of the brake booster. The operating rod 22 corresponds to a reactive member. With an operating pedal device of a by-wire type employed to electrically control a wheel brake, the reactive member, on which a predetermined reactive force acts, that is which receives the predetermined reactive force, due to an action of a reactive mechanism or the like, is connected in place of the operating rod 22.
The operating pedal 16 has a coupling position, connected with the clevis pin 26, which is formed with a sensor-mounting hole 202 with a diameter larger than that of the clevis pin 26. A load sensor 204, located in an annular space between the sensor-mounting hole 202 and the clevis pin 26, includes a cylindrical strain body or strain-triggering body 206 for detecting a load applied to thereto in a radial direction. The load sensor 204 further includes an annular case member 208 disposed outside the strain body 206, and a shaft-like member 210 disposed an area inside the strain body 206.
The case member 208 is comprised of a cylindrical inner circumferential connecting portion 208a, a cylindrical outer circumferential wall 208b, a plate-like connecting flange 208c and a positioning flange 208d, which are formed in a double-layered cylindrical structure as a whole. The connecting portion 208a, placed in an inner circumferential area thereof has an axial area to which one axial end portion of the strain body 206 (an upper end portion thereof as viewed in FIG. 21B) is integrally fixed by press fitting, welding or the like. The outer circumferential wall 208b is formed in an outer circumferential area of the connecting portion 208a so as to surround the connecting portion 208a. The connecting flange 208c has an area in which the connecting portion 208a and the outer circumferential wall 208b are integrally connected to each other at axial ends thereof. The positioning flange 208d is formed continuous or contiguous with the connecting flange 208c and protrudes radially outward from the outer circumferential wall 208b. The case member 208 is arranged such that the outer circumferential wall 208b is fitted to the sensor-mounting hole 202, and the positioning flange 208d is contacted with the operating pedal 16 on one side thereof with a leaf spring or the like (not shown) in non-dismounting fashion.
The shaft-like member 210 integrally holds the other axial end (a lower end portion in FIG. 21B) of the strain body 206 by press fitting, welding or the like, and has an insertion bore 210h through which the clevis pin 26 is extended. The clevis pin 26, the insertion bore 210h and the clevis 24 are made relatively rotatable. Thus, they are rendered operative to relatively rotate lessened in friction with the operating pedal 16 being depressed. However, bearings or bushes may be mounted in the associated component parts to reduce frictions depending on needs.
Thus, the case member 208 and the shaft-like member 210 are connected to each other via the strain body 206. When a load, externally applied to the strain body 206 in a radial direction, that is in a direction perpendicular to the axis thereof, becomes approximately zero, the respective members 206, 208 and the 210 remain under states approximately concentric to i.e. coaxial with an axis of the clevis pin 26. In contrast, if a load is radially applied to between the case member 208 and the shaft-like member 210 due to a reactive force of the operating rod 22 in accordance with depression of the operating pedal 16, the strain body 206 is shear-deformed. As a result, the case member 208 facing the operating pedal 16, displaces relative to the shaft-like member 210 in a direction (leftward as viewed in FIG. 21A) to be closer relative to the operating rod 22.
An annular space is provided between the case member 208 and the shaft-like member 210 for permitting these members to be relatively displaced in a radial direction, and shear deformation of the strain body 206 is permitted. The strain body 206 is made of metallic material such as ferritic stainless steel or the like that is elastically deformable when applied with a load in a radial direction. Thus, in accordance with depression of the operating pedal 16, the resulting operating force causes the strain body 206 to be shear-deformed. For detecting a shear strain of the strain body 206, strain detecting elements such as strain resistance elements or the like are mounted on an outer circumferential surface or inner circumferential surface of the strain body 206 in electrical connection to a control circuit section of the vehicle via the wire harness 56. Thus, the control circuit section can detect a depressed operating force based on electric signals output from the strain detecting elements.
With the vehicle operating pedal device 200 of such a structure, the pivotably connecting section 20 transmits the operating force applied to the operating pedal 16 to the operating rod 22. With the pivotably connecting section 20, the operating pedal 16 connected to the operating rod 22 via the clevis pin 26 to be pivotable relative to each other, has the sensor-mounting hole 202 to allow the cylindrical load sensor 204 to be mounted in the annular space defined between the sensor-mounting hole 202 and the clevis pin 26. This minimizes the occurrence of rotational moment such as torsion or the like, enabling the operating pedal device 200 to be formed in a simple and compact structure as a whole. In addition, the operating pedal device 200 can employ the same peripheral units, like the operating rod 22 and the clevis 24, as those of the conventional pedal device, enabling a reduction in production cost of the device.
With the vehicle operating pedal device 200 of such a structure, however, the case member 208 of the load sensor 204 is formed in the cylindrical configuration. With an input load (a reactive force in this case) F transmitted from the clevis pin 26 to the case member 208 passing through the shaft-like member 210 and the strain body 206, substantially one point of the outer circumferential wall 208b of the case member 208 is pressed against the inner peripheral surface of the sensor-mounting hole 202 to bear the input load F.
Thus, as shown in FIGS. 22A and the 22B in exaggerated manner, the case member 208 has a fear of encountering flexure deformation due to stress concentration. FIG. 22A shows the load sensor 204 remained under an unloaded state and FIG. 22 shows the load sensor 204 under a state applied with the load F. FIGS. 22A and the 22B have upper areas shown in front views and the lower areas shown in cross sectional views. Due to flexure deformation caused in the case member 208, the strain body 206 encounters undesirable deformation like bending, torsion or the like, and in alternative, the strain body 206 has a lessened deformation amount, resulting in a possibility of degraded detecting precision of the operating force.
As the operating pedal 16 pivotable about the axis of the support shaft 14 in accordance with depression of the operating pedal, further, the operating rod 22 and the operating pedal 16 are also pivoted relative to each other about the axis of the clevis pin 26. This causes the input load F to vary in applied direction, resulting in a possibility of causing the case member 208 to be displaced in a swaying i.e. rocking mode caused by a clearance between the case member 208 and the sensor-mounting hole 202. In view of this, there is a fear of occurrence of degraded detecting precision of the operating force.
If the input load F is varied in applied direction with the case member 208 remains flexure deformed, the strain body 206 becomes complicated in deforming pattern with a resultant occurrence of easily causing a variation in deforming rate as shown in FIGS. 23A and 23B in exaggerated manner. This results in further degraded detecting precision with a possibility of a lack of stability. FIG. 23A shows a case in which both the outer circumferential wall 208b of the case member 208 and the strain body 206 are encountered with flexure deformation. FIG. 23B shows another case in which the input load F is applied to the strain body 206 in a varying direction with both the outer circumferential wall 208b and the strain body 206 remained flexure deformed, under which the rest of the strain body 206 except for an acting area of the input load F is also deformed. In this case, even when the input load F is applied at the same rate, the strain detecting elements 212 and the 214 have less average strain value than those of the strain detecting elements 212 and the 214 under states shown in FIG. 23A.
With the operating pedal device 200 used in actual practice, since the input load F increases depending on a depressing stroke of the operating pedal 16, there is a fear of a difficulty occurred in correctly detecting the increased input load F, i.e., the operating force.